The present invention relates to the field of microelectromechanical systems and, more particularly, to a connector microstructure that is compliant, but yet which still allows for the effective transmission of mechanical forces at high operating frequencies.
Microelectromechanical (MEM) systems are getting a significant amount of attention in the field of optical switches. MEM technology generally involves the fabrication of small mechanical devices on a silicon substrate, together with electronic circuitry for actuating motion of the mechanical device. Surface micromachining is one type of fabrication technique for MEM systems. Surface micromachining generally entails depositing alternate layers of structural material and sacrificial material on an appropriate substrate, such as a silicon wafer, which functions as a foundation for the resulting microstructures. Various patterning operations may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructures. After the microstructures have been defined in this general manner, the various sacrificial layers are removed by exposing the microstructures and the various sacrificial layers to one or more etchants which xe2x80x9creleasesxe2x80x9d the resulting microstructures from the substrate (e.g., to allow relative movement).
A MEM-based optical system may include multiple mirror microstructures formed on a substrate for making optical connections. Each mirror microstructure may be interconnected with at least one lift assembly, one or more actuators, and one or more displacement multipliers. The lift assembly may be used to raise the mirror microstructure above the plane of the substrate and/or tilt the mirror into an appropriate position to provide a desired optical function. The actuators are attached to the substrate so as to be movable relative thereto, and provide the motive force/displacement that is used to raise/tilt these mirrors. Electrostatic actuators are commonly used in these types of systems. These types of actuators produce a short stroke displacement which may be insufficient to raise/tilt the mirror to a desired level in at least certain instances. Therefore, the noted displacement multiplier(s) is typically disposed between the actuator and its associated lift assembly to increase the displacement provided by the actuator to the lift assembly, and to thereby allow the mirror microstructure to be raised/tilted to a desired degree. One example of a displacement multiplier is disclosed in U.S. Pat. No. 6,175,170.
Displacement multipliers may be designed to produce a relatively large output based upon a relatively small input. However, displacement multipliers can become rather intricate, which increases development costs. Moreover, displacement multipliers often require a significant amount of space on a die. Since there is only a fixed amount of space within a die for fabrication of the microelectromechanical system, the use of one or more displacement multipliers may reduce the mirror density within the die. Although this may be acceptable for certain applications, a higher mirror density may be desirable for other applications. Therefore, it would be desirable to achieve displacement multiplication for a microelectromechanical system in a manner that allows for increased mirror density.
A tether or the like may be disposed within the interconnection between a mirror elevator and the actuator(s). For instance, an actuator or a plurality of actuators may be interconnected with an input to a displacement multiplier, and the tether may interconnect the output of the displacement multiplier with the mirror elevator. This mirror elevator may have a free end that moves away from and toward the substrate, depending upon the direction of the movement of the actuator(s). This then raises and/or tilts a mirror that may be interconnected with the elevator.
One previously contemplated configuration for the above-noted tether was to form the same from a single layer of a structural material in a surface micromachined optical system. This resulted in the tether being flexible.
Generally, the present invention is embodied in a microelectromechanical (MEM) system having what may be characterized as a lift assembly that is elevatable from a substrate in response to an input displacement that is typically (although not required to be) at least generally parallel with the substrate. The substrate is one that is appropriate for MEM applications. The lift assembly is operable to move an end of an elevation member of the lift assembly at least generally away from or toward the substrate in response to an input displacement, where the movement of the elevation member""s free end at least generally away from or toward the substrate is xe2x80x9cmultipliedxe2x80x9d without requiring the use of a separate displacement multiplier. Any appropriate microstructure may be interconnected with this elevation member and for any appropriate application, including without limitation a mirror microstructure for any appropriate optical application (e.g., optical switches, attenuators, multiplexers, and de-multiplexers).
A MEM system of a first aspect of the present invention is preferably fabricated by surface micromachining, although other MEM fabrication techniques or combination of fabrication techniques may be utilized as desired/required. In any case, the MEM system includes: a substrate; any appropriate actuator that is movably interconnected with the substrate in any appropriate manner; a first elevation member that is interconnected with the substrate at a first location (e.g., at one end of the first elevation member, although the first elevation member could be interconnected with the substrate at an intermediate location that is between a pair of its ends) and a free end that is movable at least generally away from or toward the substrate, depending upon the directional movement of the actuator; and a coupling or xe2x80x9ctetherxe2x80x9d that is disposed between and interconnects the actuator to a portion of the first elevation member that is able to move at least generally away from or toward the substrate. Any configuration may be used for this tether. What is important is that the tether attaches to the first elevation member at a location that is between the first location where the first elevation member is interconnected with the substrate and a free end thereof. The benefit of attaching the tether to a location that is between where the first elevation member is interconnected with the substrate and a free end of the first elevation member is that, by adjusting the attachment location along the length of the first elevation member, the displacement of the first elevation member""s free end may be altered (i.e., multiplied/amplified) withrespect to the input displacement without requiring the use of a separate displacement multiplier. Since the MEM system of the first aspect does not require the use adisplacement multiplier to produce a multiplied lift for the first elevation member (that is often necessary in various optical applications and possibly others as well), more room on the substrate is available for other microstructures. Accordingly, a higher packing density of microstructures (e.g., mirrors) may be achieved on the substrate.
Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in the first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The first elevation member in the case of the first aspect again is interconnected with the substrate at a first location and has a free end that is operable to move at least generally away from the substrate in response to an input displacement. Any type of motion of the free end of the first elevation member may be utilized and in any manner that is at least generally away from or toward the substrate. In one embodiment, the free end moves along a path that is at least generally within a plane that is at least generally perpendicular to the substrate. In another embodiment, the free end moves along a path that is at least generally within a plane that is disposed in non-perpendicular relation to the substrate. In another embodiment the movement of the free end of the first elevation member is not confined to being within a reference plane.
Any way of interconnecting the first elevation member with the substrate in a manner that allows a free end thereof to at least generally move away from or toward the substrate may be utilized. The first elevation member may be compliantly attached to the substrate such that the portion of the first elevation member between the first location and its free end is able to rotate or xe2x80x9cpivotxe2x80x9d about this connection point, and thus allow this free end to move at least generally away from or toward the substrate with a displacement that has both a component that is lateral to the substrate and a component that is perpendicular to the substrate (e.g., along an arcuate path). In one embodiment, a portion of the first elevation member is connected directly to the substrate at the first location, and the first elevation member xe2x80x9cbendsxe2x80x9d or flexes to provide the desired motion for the free end of the first elevation member at least generally away from or toward the substrate. In this configuration, the first elevation member may have first and second cross-sectional areas along its length. As will be appreciated, if the entire first elevation member is made of the same material (e.g., polycrystalline silicon) and in the same structural layer, the portion of the first elevation member with the smaller cross-sectional area will have a smaller moment of inertia about a particular axis and, thus, will be less stiff than the larger cross-sectional area portion. Accordingly, this smaller cross-sectional portion may be formed over that portion of the first elevation member that is attached to the substrate and act as what may be characterized as an integral flexible/compliant hinge, thereby allowing the free end of the first elevation member to move at least generally away from or toward the substrate.
In another embodiment associated with the first aspect, a separate moving or movable hinge (e.g., multiple and discrete parts that are movably interconnected) may be used to movably interconnect the first elevation member with the substrate such that the free end of the first elevation member is able to move at least generally away from or toward the substrate in the desired/required manner. Any structure for establishing this hinge and/or manner of interconnecting the hinge/hinge members with the substrate and/or first elevation member may be utilized. In yet another embodiment of the first aspect, a compliant or flexible hinge of sorts may be used to movably interconnect the first elevation member and the substrate. This compliant hinge may be anchored to the substrate (e.g., by passing through one or more structural layers of a surface micromachined microelectromechanical system), and may also be appropriately anchored to the first elevation member. Accordingly, this compliant hinge may have a stiffness that is less than that of the first elevation member (and preferably a stiffness less than that of its anchor as well) such that a force acting on the first elevation member may bend this compliant hinge before bending the first elevation member. As will be appreciated, this compliant hinge may be formed so that it has a first stiffness in one direction and a second stiffness in a second direction that is greater than the first stiffness. For example, the compliant hinge may be formed as a strip with a rectangular cross-section that has a width greater than its height or thickness. In this embodiment, the compliant hinge will be less stiff about an axis that is parallel with its width axis, while remaining stiffer in the axis perpendicular to its width. In this regard, the compliant hinge may permit the first elevation member to be pivoted in effect about only a single axis so as to allow for controlled movement of the compliant hinge and thereby the first elevation member (as well as any microstructure interconnected therewith).
In order to move a free end of the first elevation member at least generally away from or toward the substrate, the MEM system associated with the first aspect again includes an actuator that is operable to produce an at least generally lateral movement relative thereto (e.g., so as to move at least generally across the substrate). Any appropriate type of actuator may be utilized (e.g., electrostatic comb actuator, a capacitive-plate electrostatic actuator, a thermal actuator, a movable-electrode electrostatic actuator, a piezoelectric actuator, an electromagnetic actuator and a magnetic actuator), and any appropriate way of interconnecting the same with the substrate to allow relative movement in the desired/required manner may be utilized as well. Moreover, multiple actuators may be used and interconnected with a single coupling or tether to exert the desired force on the first elevation member to move a free end thereof at least generally away from or toward the substrate. For example, a pair of actuators may be used in parallel, where the separate actuators are coupled by a laterally moveable yoke formed on the substrate. In this regard, the tether that interconnects the actuators with the elevation member may be interconnected (directly or indirectly) to this yoke so the combined force of the separate actuators is applied to the first elevation member through the tether.
The actuator microstructure is interconnected with the first elevation member and operable to provide the displacement that has the effect of moving a free end of the first elevation member at least generally away from or toward the substrate in the subject first aspect. In this regard, a laterally movable output of the actuator microstructure may be transferred to the first elevation member by a coupling or xe2x80x9ctetherxe2x80x9d as noted above, where one end of the tether may be attached directly to the actuator microstructure and another end of the tether may be directly attached to the first elevation member between the first location where the first elevation member is interconnected with the substrate and a free end thereof That is, in one embodiment there is no xe2x80x9cintermediatexe2x80x9d structure in the interconnection of the actuator with the connector (e.g., no displacement multiplier). When the actuator microstructure is engaged, such as to produce an xe2x80x9cin-planexe2x80x9d or lateral displacement, the tether exerts a force on the first elevation member and thereby moves a free end thereof at least generally away from or toward the substrate. In another embodiment, an actuator may be used in conjunction with a displacement multiplier where the first elevation member is attached to the output of a displacement multiplier by the noted tether and where the input of the displacement multiplier is interconnected with the actuator.
The tether in the case of the subject first aspect is disposed or located at least somewhere between the actuator and the first elevation member, and interconnects the actuator to a location that is between the first location where the first elevation member is interconnected with the substrate and a free end thereof. As noted, the tether may be used to exert a force on the first elevation member so as to move a free end thereof at least generally away from the substrate when the actuator produces an in-plane or lateral displacement. In addition, the tether may be used to move the free end of the first elevation member back at least toward the plane of the substrate when the actuator is disengaged or moved in an opposite direction than that which moved the free end at least generally away from the substrate. Typically, the microelectromechanical system of the first aspect will use both directions of motion of the first end of the first elevation member. For instance, a pair of first elevation members may be interconnected with a mirror microstructure. Movement of the first free end of both of these first elevation members at least generally away from the substrate may be used to achieve one position for the mirror microstructure. Thereafter, the free end of one of the first elevation members may be moved at least generally away from or toward the substrate to tilt the mirror microstructure in a desired manner. Moreover, the first ends of both first elevation members may be moved at least generally away from or toward the substrate to tilt the mirror microstructure in a desired manner or to xe2x80x9clowerxe2x80x9d the mirror microstructure.
Any appropriate configuration for the first elevation member may be utilized by the first aspect of the present invention, as well as any manner of movably interconnecting the same with the substrate. For instance, the first elevation member could be a single simple beam. Another option would be to define the first elevation member by a plurality of legs or beams that are appropriately interconnected. One or more cross beams may extend between and interconnect two or more of these legs to provide a desired degree of rigidity to the first elevation member.
To produce a multiplied displacement in the first elevation member with a component that is at least generally away from or toward the substrate in the case of the first aspect, a first end of the tether may be interconnected with the first elevation member at a point that is between the first location where the same is interconnected with the substrate and a free end thereof, and a second end of the tether may be interconnected with the actuator. Further, the system may be arranged such that the actuator and the end of the tether interconnected therewith (the second end) are maintained in a fixed positional relationship during movement of the actuator such that the actuator and the second end of the tether move in a one-to-one ratio. Contrast this with situations where a displacement multiplier interconnects the actuator with the noted second end of the tether. In this case, the second end of this tether (attached to the output of the displacement multiplier) would move more than the actuator because of the multiplication provided by the displacement multiplier.
The tether associated with the first aspect may be attached anywhere between a free end of the first elevation member and the first location where the first elevation member is interconnected with the substrate, such that the tether transmits the displacement from the actuator to the first elevation member. Therefore, when the actuator is moved relative to the substrate (whether actively by an appropriate signal, passively by a spring force from one or more sources, by a combination thereof, or in any other manner), the tether may exert a force on the first elevation member, causing the first elevation member to pivot with respect to the substrate at least generally at/about the first location. As will be appreciated, this pivoting produces an angular displacement of the first elevation member and, by moving the tether attachment point on the first elevation member closer to the pivot point, a greater angular displacement of the first elevation member can be obtained using the same input displacement. Accordingly, depending on the length of the first elevation member, the length of the tether and the displacement stroke of the actuator, a displacement of a free end of the first elevation member that is greater than the input displacement of the actuator may be produced.
A second aspect of the present invention is embodied in a microelectromechanical system that includes what may be characterized as a lever or a lever assembly that is interconnected with a substrate that is used in the fabrication of the microelectromechanical system. The coupling is interconnected with the lever at a second location that is disposed between a first free end of the lever (xe2x80x9cfreexe2x80x9d in the sense that it is able to move relative to the substrate) and a first location where the lever is interconnected with the substrate (e.g., a part of the lever that does not move laterally relative to the substrate or in a dimension that is at least generally parallel with the substrate, such as by being anchored to the substrate). This first location may define a pivot point or axis of sorts. In any case, a force is exerted on the coupling, which is then transferred to the lever at the second location where the coupling interfaces with the lever. The first free end of the lever then moves relative to the substrate in response to the application of this force to the lever.
Various refinements exist of the features noted in relation to the second aspect of the present invention. Further features may also be incorporated in the second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The attachment of the coupling to the lever at the second location that is between its first free end and the first location where the lever is interconnected with the substrate amplifies the amount that the first free end of the lever moves in response to a certain lateral movement of an opposite end of the coupling, in comparison to attaching the coupling directly to the first free end of the lever. For instance, an actuator assembly (e.g., one or more actuator microstructures) may be interconnected with an end of the coupling that is opposite that which interfaces with the lever at the second location in this second aspect. Assume that the stroke of the actuator assembly is fixed at a first distance. For this same first distance, a variety of different displacements of the first free end of the lever may be realized by changing the attachment point of the coupling to the lever. Moving the attachment point of the coupling to the lever so as to be closer to the first location amplifies the displacement of the first free end of the lever for the same fixed displacement of the actuator assembly.
Any configuration for the lever may be utilized in relation to the second aspect. For instance, the lever may be defined by single beam or may be defined by a plurality beams that are structurally interconnected. A single coupling may be interconnected with a multi-beam lever structure so as to simultaneously move each of the various beams (e.g., by attaching to an interconnecting beam). Multiple couplings could also be utilized.
Any appropriate way of establishing the above-noted xe2x80x9cfirst locationxe2x80x9d on the lever may be utilized in relation to the second aspect. For instance, the lever may be anchored to an underlying structure of the microelectromechanical system at the first location, such as the substrate. One way to characterize the lever is that the same is movably interconnected with another portion of the microelectromechanical system, for instance by using a multi-piece hinge, pivot, or bearing configuration, or by using one or more compliant members and/or compliant properties (e.g., to allow for a certain degree of flexure or the like, to in turn allow for the desired movement of the first free end of the lever relative to the substrate).
Movement of the first free end of the lever relative to the substrate may be in any direction and along any appropriate path. In one embodiment, the first free end of the lever moves at least generally away from the substrate. This movement may be within a reference plane that is at least generally perpendicular to the substrate, within a reference plane that is disposed in non-perpendicular relation to the substrate, or in any manner that is at least generally away from or toward the substrate (e.g., the movement of the first free end need not be confined to being within a reference plane). In another embodiment of the subject second aspect, the first free end of the lever moves within a reference plane that is at least generally parallel with the substrate.
The third through the sixth aspects generally relate to the identification that the use of a flexible coupling or tether to transfer motion from an actuator assembly to a lever may adversely affect one or more aspects of a microelectromechanical system that uses such a lever in at least certain applications (for instance, optical). Consider the case where a lever (of any appropriate configuration, and including for example a single beam or a plurality of appropriately interconnected beams) is interconnected with a substrate that is appropriate for microelectromechanical applications, that this interconnection allows for movement of a first end of the lever at least generally about a first location, where a microstructure(s) (e.g., a mirror) is interconnected with a portion of this lever that is able to move relative to the substrate, and where an elongate tether or coupling interconnects (directly or indirectly) the lever with an actuator assembly (e.g., one or more actuators that are appropriate for microelectromechanical applications). When the actuator assembly moves relative to the substrate, to in turn move both the tether and the first free end of the lever relative to the substrate, the magnitude of the total external forces that are experienced by the tether (e.g., an actuation force (including a resultant force) that is intended to move the tether from one position to another; inertial forces from movement of the lever and any microstructure interconnected therewith), the manner in which these external forces are exerted on the tether (e.g., how abruptly the actuation force is terminated), or both may be such that a tether of insufficient stiffness would tend to flex or bow between its two opposite ends. Any such elastic deformation or buckling of the tether may adversely affect the control of the movement of the microstructure(s) that is interconnected with the movable portion of the lever. Not only could the transmission of the actuation force to the microstructure interconnected with the lever be somewhat delayed by any significant amount of flexing of the tether, but a flexed tether would eventually release the elastic energy stored therein to either xe2x80x9cslapxe2x80x9d or accelerate the interconnected microstructure in the direction of motion or otherwise cause the interconnected microstructure to vibrate or oscillate after the motion of the actuator assembly has been terminated. The third through the sixth aspects of the present invention address the identification of this potential problem.
A third aspect of the present invention is embodied in a microelectromechanical (MEM) system having a lever that is interconnected with but movable relative to a substrate in response to an input displacement that is typically, at least generally, parallel with the substrate. The substrate is one that is appropriate for use in the fabrication of microelectromechanical systems. A free end of the lever moves at least generally about a first location (e.g., where the lever is anchored to the substrate or otherwise movably interconnected with the substrate) and relative to the substrate in response to an input displacement. Any appropriate microstructure may be interconnected with any portion of the lever that is movable relative to the substrate and for any appropriate application, including without limitation a mirror microstructure for optical applications.
The MEM system of the third aspect of the present invention is preferably fabricated by surface micromachining, although other fabrication techniques or combination of fabrication techniques may be utilized as desired/required. In any case, the MEM system of the third aspect includes a substrate, an actuator assembly that is movably interconnected with the substrate in any appropriate manner, a first lever that is interconnected with the substrate for movement at least generally about a first location and that has a first free lever end that is movable relative to the substrate at least generally about the first location, and an elongate coupling or xe2x80x9ctetherxe2x80x9d that is disposed between and interconnects the actuator assembly and the first lever (either directly or indirectly). Any configuration may be used for this tether. What is important is that the tether is sufficiently stiff so as to withstand the external forces applied thereto without substantially bowing or buckling.
The benefit of using a tether that is sufficiently stiff to withstand the external forces that may be applied to the tether due/in response to a movement of the actuator assembly (including how the motion of the actuator assembly is initiated and/or maintained, as well as how the motion of the actuator assembly is terminated) in accordance with the third aspect is that a slapping and/or oscillatory effect associated with less stiff tethers is eliminated or at least significantly reduced. For example, a tether that will flex or bow when exposed to external forces of at least a certain magnitude will result in elastic energy being stored within the tether. When this elastic energy is released, this may cause a free end of the lever to accelerate in an undesired manner, may cause this free end of the lever to vibrate or oscillate, or both. The release of this elastic energy may significantly adversely affect the ability to precisely control the operation of the microelectromechanical system, may cause undesired contact between components of the microelectromechanical system and possibly resulting structural damage, or both. Using a stiff tether (such that no significant elastic energy is stored in the tether as a result of typical external forces being exerted thereon) in accordance with the third aspect addresses these types of deficiencies. Stiff tethers also may allow for increasing the switching speed in the case where the third aspect is used in an optical application (e.g., when a mirror microstructure is interconnected with a portion of the first lever that is movable relative to the substrate).
Various refinements exist of the features noted in relation to the third aspect of the present invention. Further features may also be incorporated in the third aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Initially, the features discussed above in relation to the first and second aspects may be utilized in the subject third aspect in any combination. Any appropriate configuration may be used for the lever that is associated with the third aspect that provides the desired stiffness. Moreover, any way of interconnecting the lever with the substrate to allow its first free lever end to move relative to the substrate may be utilized as well. Movement of the first free lever end relative to the substrate may be in any direction and along any appropriate path. In one embodiment, the first free lever end moves at least generally away from or toward the substrate, depending upon the direction of motion of the actuator assembly. This type of movement may be within a reference plane that is at least generally perpendicular to the substrate, within a reference plane that is disposed in non-perpendicular relation to the substrate, or in any manner that is at least generally away from or toward the substrate (e.g., the movement of the first free lever end need not be confined to being within a reference plane). In another embodiment of the subject third aspect, the first free lever end moves within a reference plane that is at least generally parallel with the substrate.
The tether in the case of the third aspect may be used to pull the first free lever end away from the substrate when the actuator produces an in-plane displacement or one that is at least generally parallel with the general lateral extent of the substrate (e.g., the actuator moves at least generally horizontally). In addition, the tether may be used to lower the first free lever end back toward the substrate. In accordance with the third aspect of the present invention, the tether has a stiffness that is sufficient to withstand external forces (e.g., an actuation force, inertial forces) that are applied to the tether due to or as a result of an acceleration of the actuator assembly (positive or negative), while moving the first free lever end relative to the substrate. xe2x80x9cWithstandxe2x80x9d in this context means without substantially flexing or bending.
The actuator assembly that is associated with the third aspect may include one or more actuators that are appropriate for microelectromechanical applications. The actuation force that is exerted on the tether may be active, passive, or some combination of active and passive. For instance, an active force may be generated by transmitting an appropriate signal to the actuator assembly. A passive force, on the other hand, may involve the release of stored or potential energy. For instance, energy may be stored in the interconnecting structure between the actuator assembly and the substrate, and the release of this energy may be characterized as being part of or contributing to the actuation force. Energy that is stored in one or more other components of the microelectromechanical system of the third aspect may also contribute to the total actuation force that is exerted on the coupling (e.g., in a separate compliant member that interconnects the two ends of the tether to the relevant structure).
A fourth aspect of the present invention is embodied in a microelectromechanical system that is fabricated using an appropriate substrate. The system includes a lever that is somehow movably interconnected with the substrate at a first location such that a first free lever end of the lever is able to move relative to the substrate at least generally about the first location. An actuator assembly is interconnected with the substrate for movement at least generally along a first path. An elongate coupling interconnects the lever and this actuator assembly. One end of the elongate coupling is interconnected (directly or indirectly) with the actuator assembly, while the opposite end of the elongate coupling is interconnected (directly or indirectly) with a portion of the lever that is able to move relative to the substrate in a direction that depends upon the direction of the actuation force being exerted on the elongate coupling by/through a movement of the actuator assembly relative to the substrate. Movement of the first free lever end relative to the substrate in a first direction is accomplished by the actuator assembly moving relative to the substrate in a second direction that results in the exertion of what may be characterized as a first actuation force on the elongate coupling that is transferred to the lever. Movement of the first free lever end relative to the substrate in a third direction (different from the first direction) is accomplished by the actuator assembly moving relative to the substrate in a fourth direction (different from the second direction) that results in the exertion of what may be characterized as second actuation force on the elongate coupling that is transferred to the lever. The elongate coupling is configured to have a certain minimum buckle strength between opposite ends of the elongate coupling that defines its length. The maximum actuation force that is exerted on the elongate coupling as a result of movement of the actuator assembly relative to the substrate during operation of the microelectromechanical system has at least a first component that is directed along the first path. The noted minimum buckle strength of the elongate coupling is greater than that the magnitude of this first component in the case of the fourth aspect.
Various refinements exist of the features noted in relation to the fourth aspect of the present invention. Further features may also be incorporated in the fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Initially, any of the features discussed above in relation to the first and second aspects may be incorporated in the subject fourth aspect as well, alone or in any combination. Although the fourth aspect may be appropriate for any number of applications, in one embodiment a mirror or the like is interconnected with a portion of the lever that is able to move at least generally away from and toward the substrate (e.g., to lift and/or tilt a mirror relative to the substrate by interconnecting the mirror with a portion of the lever that is able to move relative to the substrate).
Any appropriate configuration may be used for the lever that is associated with the fourth aspect. Moreover, any way of interconnecting the lever with the substrate may be utilized so as to allow the first free lever end to move relative to the substrate at least generally about the first location in the case of the fourth aspect (e.g., via one or more compliant members, via a multi-piece pivot or hinge, via a configuration of that portion of the lever that is interconnected with the substrate). Movement of the first free end of the lever relative to the substrate may be in any direction and along any appropriate path. In one embodiment, the first free lever end moves at least generally away from or toward the substrate, depending upon the direction of motion of the actuator assembly. This type of movement may be within a reference plane that is at least generally perpendicular to the substrate, within a reference plane that is disposed in non-perpendicular relation to the substrate, or in any manner that is at least generally away from or toward the substrate (e.g., the movement of the first free lever end need not be confined to being within a reference plane). In yet another embodiment of the subject fourth aspect, the first free lever end moves within a reference plane that is at least generally parallel with the substrate.
The actuator assembly that is associated with the fourth aspect may include one or more actuators that are appropriate for microelectromechanical applications. The actuation force applied to the elongate coupling may be active, passive, or some combination of active and passive. An active actuation force may be generated by transmitting an appropriate signal to the actuator assembly. A passive actuation force, on the other hand, may involve the release of stored energy. For instance, energy may be stored in the interconnecting structure between the actuator assembly and the substrate, and the release of this energy may be characterized as being part of the actuation force. Moreover, energy may be stored in other portions of the microelectromechanical system of the fourth aspect (e.g., a compliant member that interconnects the elongate coupling and the lever), and the release of this energy may be characterized as being part of the actuation force.
In one embodiment of the fourth aspect, the elongate coupling has a length of at least about 750 microns, and in another embodiment a length of at least about 1,300 microns (again, measured between its two ends). In another embodiment, the component of the actuation or restoring force that is directed along the first path of movement of the actuator assembly is at least about 20 xcexcN. One way in which the desired buckle strength may be realized for the elongate coupling utilized by the fourth aspect is by forming the elongate coupling from multiple, spaced structural layers that are rigidly interconnected at a plurality of intermediate locations between the opposite ends of the elongate coupling.
There are a number of additional ways to characterize the elongate coupling of the fourth aspect being configured to have the above noted buckle strength. One is that the elongate coupling is stiff. Others are that the movement, speed, acceleration, or any combination thereof, of the first free lever end relative to the substrate is at least substantially solely controlled by external forces that are exerted on the elongate coupling. That is, no significant portion of the forces that cause the first free lever end to move relative to the substrate are due to any internal forces that may exist within the elongate coupling due to being placed in compression as a result of the application of the actuation force thereto through movement of the actuator assembly in the relevant direction. Yet another is that a stiffness of the elongate coupling is such that the elongate coupling undergoes at least substantially no elastic deformation when the actuator assembly exerts the actuation force on the elongate coupling to move the first free lever end relative to the substrate through movement of the actuator assembly in the relevant direction.
A fifth aspect of the present invention is embodied in a microelectromechanical system that is fabricated using an appropriate substrate. The system includes a lever that is somehow interconnected with the substrate such that a first free lever end of the lever is movable relative to the substrate at least generally about a first location. An actuator assembly is interconnected with the substrate for movement at least generally along a first path. An elongate coupling interconnects the lever and the actuator assembly. This elongate coupling is formed by a plurality of vertically spaced structural layers that are rigidly interconnected at typically a plurality of spaced locations (e.g., formed via surface micromachining). One end of the elongate coupling is interconnected (directly or indirectly) with the actuator assembly, while the opposite end of the elongate coupling is interconnected (directly or indirectly) with a portion of the lever that is able to move relative to the substrate in a direction that depends upon the direction of the actuation force being exerted on the elongate coupling by/through a movement of the actuator assembly. Movement of the first free lever end relative to the substrate in a first direction is accomplished by a movement of the actuator assembly in a second direction that results in the exertion of what may be characterized as a first actuation force on the elongate coupling that is transferred to the lever. Movement of the first free lever end relative to the substrate in a third direction (different from the first direction) is accomplished by a movement of the actuator assembly in a fourth direction (different that the second direction) that results in the exertion of what may be characterized as second actuation force on the elongate coupling that is transferred to the lever.
Various refinements exist of the features noted in relation to the fifth aspect of the present invention. Further features may also be incorporated in the fifth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Initially, any of the features discussed above in relation to the first and second aspects may be incorporated in the subject fifth aspect as well, alone or in any combination. Although the fifth aspect may be appropriate for any number of applications, in one embodiment a mirror or the like is interconnected with a portion of the lever that is able to move at least generally away from and toward the substrate (e.g., to lift and/or tilt a mirror relative to the substrate by interconnecting the mirror with a portion of the lever that is able to move relative to the substrate).
Any appropriate configuration may be used for the lever that is associated with the fifth aspect. Moreover, any way of interconnecting the lever with the substrate may be utilized so as to allow a free end thereof to move relative to the substrate at least generally about the first location in the case of the fifth aspect (e.g., via one or more compliant members, via a multi-piece pivot or hinge, via a configuration of that portion of the lever that is interconnected with the substrate). Movement of the first free lever end relative to the substrate may be in any direction and along any appropriate path. In one embodiment, the first free lever end moves at least generally away from or toward the substrate, depending upon the direction of motion of the actuator assembly. This type of movement may be within a reference plane that is at least generally perpendicular to the substrate, within a reference plane that is disposed in non-perpendicular relation to the substrate, or in any manner that is at least generally away from or toward the substrate (e.g., the movement of the first free lever end need not be confined to being within a reference plane). In another embodiment of the subject fifth aspect, the first free lever end moves within a reference plane that is at least generally parallel with the substrate.
The actuator assembly that is associated with the fifth aspect may include one or more actuators that are appropriate for microelectromechanical applications. The actuation force that is applied to the elongate coupling may be active, passive, or some combination of active and passive. An active actuation force may be generated by transmitting an appropriate signal to the actuator assembly. A passive force, on the other hand, may involve the release of stored energy. For instance, energy may be stored in the interconnecting structure between the actuator assembly and the substrate, and the release of this energy may be characterized as being part of the actuation force. Moreover, energy may be stored in other portions of the microelectromechanical system of the fifth aspect (e.g., a compliant member that interconnects the elongate coupling and the lever), and the release of this energy may be characterized as being part of the actuation force.
In one embodiment of the fifth aspect, the elongate coupling has a length of at least about 750 microns, and in another embodiment a length of at least about 1,300 microns (again, measured between its two ends). Forming the elongate coupling of the fifth aspect from multiple structural layers may provide a certain minimum buckle strength between the opposite ends of the coupling. In this regard, the design of the microelectromechanical system of the fifth aspect may be such that actuator assembly of the fifth. aspect exerts a maximum magnitude of the actuation force on the elongate coupling, and that has at least a first component that is directed along the first path. The noted minimum buckle strength of the elongate coupling is preferably greater than that the magnitude of this first component in this particular embodiment of the fifth aspect. In one embodiment, the component of the actuation force that is directed along the first path of movement of the actuator assembly is at least about 20 xcexcN.
There are a number of additional ways to characterize the elongate coupling of the fifth aspect being configured to have the noted buckle strength. One is that the elongate coupling is stiff. Others are that the movement, speed, acceleration, or any combination thereof, of the first free lever end relative to the substrate is at least substantially solely controlled by external forces that are exerted on the elongate coupling. That is, no significant portion of the forces that cause the first free lever end to move relative to the substrate are due to any internal forces that may exist within the elongate coupling due to being placed in compression as a result of the application of the actuation force thereto through a movement of the actuator assembly in the relevant direction. Yet another is that a stiffness of the elongate coupling is such that the elongate coupling undergoes at least substantially no elastic deformation when the actuator assembly exerts the actuation force on the elongate coupling to move the first free lever end relative to the substrate through a movement of the actuator assembly in the relevant direction.
A sixth aspect of the present invention is directed to a method for operating a microelectromechanical system that is fabricated using an appropriate substrate, and that includes an elongate coupling that is interconnected with a lever. This method includes accelerating the elongate coupling. Accelerating the elongate coupling results in the elongate coupling being placed in compression at least at some point in time. This acceleration also moves a first lever end of the lever relative to the substrate based on its interconnection with the elongate coupling. The movement of the first lever end relative to the substrate is at least substantially solely controlled by external forces that are exerted on said elongate coupling. That is, no significant portion of the forces that cause the first lever end to move relative to the substrate are due to any internal forces that may exist within the elongate coupling due to being placed in compression by an acceleration of the elongate coupling.
Various refinements exist of the features noted in relation to the sixth aspect of the present invention. Further features may also be incorporated in the sixth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The acceleration of the elongate coupling may be provided by or as a result of a movement of an actuator assembly relative to the substrate. One or more actuators of any appropriate type may be utilized by such an actuator assembly. Movement of the actuator assembly may be active (e.g., by applying an appropriate signal to the actuator assembly), passive (e.g., via a return force that is exerted on the actuator assembly by a suspension that movably interconnects the actuator assembly with the substrate), or some combination thereof. There may be one or more other contributing sources to the acceleration of the elongate coupling as well. For instance, elastic energy may be stored in a compliant member that may be used to interconnect one or both ends of the elongate coupling with adjacent portions of the system (e.g., with the lever; with the actuator assembly; with a displacement multiplier that is disposed between and that interconnects the actuator assembly and the elongate coupling).
Movement of the first lever end relative to the substrate in the case of the sixth may be in any direction and along any appropriate path. In one embodiment, the movement of the first lever end is at least generally within a reference plane that is at least generally perpendicular to the substrate. In another embodiment, the movement of the first lever end is at least generally within a reference plane that is disposed in non-perpendicular relation to the substrate. In yet another embodiment, the movement of the first lever end is at least generally parallel with a lateral extent of the substrate. Typically the first lever end moves along an at least generally arcuate path relative to the substrate, although other types of movements may be utilized.
One way in which the movement of the first lever end relative to the substrate in the case of the sixth aspect may be accomplished by using only external forces that are exerted on the elongate coupling, is by forming the elongate coupling to be sufficiently stiff or such that it does not buckle to any significant degree when accelerated. In this regard, features discussed above in relation to the fifth aspect may be utilized by the subject sixth aspect as well.
A seventh aspect of the present invention is embodied in a microelectromechanical system that is fabricated utilizing an appropriate substrate. A lever assembly of any appropriate configuration is interconnected with this substrate such that at least part thereof is able to move both at least generally away from and toward the substrate, depending upon the direction of the force being exerted on the lever assembly. In this regard, the microelectromechanical system further includes an actuator assembly that is interconnected with the substrate for movement along a first path, a coupling that is appropriately interconnected (directly or indirectly) with this actuator assembly, and a connector that is attached to the lever assembly and that is also attached to the coupling. As such, movement of the actuator assembly relative to the substrate is transmitted to the lever assembly through the coupling and the connector.
The connector associated with the seventh aspect includes first and second connector ends and first and second flex link assemblies. The second connector end is located between the first connector end and the actuator assembly, and the coupling is attached to the connector at least at the first connector end. Both the first and second flex link assemblies extend between and interconnect the first and second connector ends. Finally, the connector includes a first interconnect that extends between and interconnects the first flex link assembly and one portion of the lever assembly, as well as a second interconnect that extends between and interconnects the second flex link assembly and another portion of the lever assembly.
Various refinements exist of the features noted in relation to the seventh aspect of the present invention. Further features may also be incorporated in the seventh aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The lever assembly may be characterized as an elevation structure, which may be of any appropriate configuration. The lever assembly may be of any configuration or structure that may be interconnected with the substrate so that at least a portion thereof is able to move at least generally away from or toward the substrate, depending upon the direction of the forces being exerted thereon. Any appropriate device(s) may be interconnected with this elevation structure (e.g., a mirror microstructure) and in any appropriate manner. In one embodiment, a cross beam extends between and interconnects laterally spaced portions of the lever assembly, and the connector is located somewhere between the location of this cross beam and the location where the lever assembly is movably interconnected with the substrate. That is, the first connector end is spaced from the cross beam in this embodiment, which may be characterized as a free end of the elevation structure. As such, the various features discussed above in relation to the first, second, and third aspects may be utilized by this seventh aspect as well, alone or in any combination.
Any way of movably interconnecting the lever assembly with the substrate may be utilized. Surface micromachining may be used to define at least part of the microelectromechanical system of the seventh aspect. In this case, the lever assembly may be interconnected with the substrate by a compliant flexure to allow a free end of the lever assembly to move at least generally away from or toward the substrate, depending upon the direction of movement of the actuator assembly. Each compliant flexure may be attached to a corresponding portion of the lever assembly and also attached to the substrate by an appropriate anchor.
The first and second connector ends and the first and second flex link assemblies of the connector that are utilized by the seventh aspect may be characterized as collectively defining a frame having a closed perimeter. This frame is at least generally rectangular in one embodiment. Other frame configurations/profiles may be appropriate (e.g., diamond-shaped). In any case, the first interconnect could thereby extend from one side of the connector frame to one portion of the lever assembly, while the second interconnect could extend from an opposite side of the connector frame to another portion of the lever assembly. Another way of characterizing the general configuration of the connector associated with the seventh aspect is that the first and second flex link assemblies may be disposed at least generally parallel with the coupling, while the first and second connector ends may be disposed at least generally transverse to the coupling. Other relative orientations may be appropriate.
Surface micromachining may be used to fabricate all or part of the microelectromechanical system of the seventh aspect of the present invention. In one embodiment, the connector is formed in a single level by surface micromachining. In another embodiment, the connector and a portion of the lever assembly that is interconnected with the connector are fabricated at a common level by surface micromachining. In yet another embodiment, a portion of the lever assembly that is interconnected with the connector is fabricated at one level by surface micromachining, while the connector is fabricated at a different level (e.g., xe2x80x9chigherxe2x80x9d or a level that is located further from the substrate) by surface micromachining.
There are a number of options in relation to how the coupling interfaces with the connector in the seventh aspect. In one embodiment, the coupling is attached to both of the first and second connector ends. Another embodiment has the sole interconnection between the coupling and the connector being at the first connector end. In this case, it may be desirable to have a supporting beam that extends between the first and second connector ends.
The first and second interconnects may be exposed to a torsional force by the application of a pulling or pushing force on the coupling in the case of the seventh aspect. This torsional force may place a tensile force on the entirety of the first and second flex link assemblies. In one embodiment, the first and second interconnects are disposed along a common reference axis that is at least generally transverse to the coupling. Other relative orientations may be utilized for the first and second interconnects. For instance, the first and second interconnects each may be disposed at an angle relative to a reference axis that is transverse to the coupling. Locationally, the first and second interconnects may each merge with the first and second flex link assemblies, respectively, at a location that is xe2x80x9cmidwayxe2x80x9d between the first and second connector ends. However, each of the first and second interconnects may merge with the first and second flex link assemblies, respectively, at other locations between the first and second connector ends. For instance, the first and second interconnects may merge with the first and second flex link assemblies, respectively, at different locations between the first and second connector ends. Stated another way and considering that the coupling defines a longitudinal dimension, the first and second interconnects may be longitudinally offset relative to each other.
The actuator assembly may move in first and second directions along the first path in the case of the seventh aspect. Movement in the first direction may be utilized to move the free end of the lever assembly at least generally away from the substrate. Movement in the second direction may be utilized to move the noted free end(s) at least generally toward the substrate. Part of the connector may be in compression and part of the connector may be in tension, regardless of whether the actuator assembly is moving in the first or second direction. Consider the case where the actuator assembly is moving in the first direction and which places the coupling in tension. In this case, that portion of the first and second flex link assemblies that is between the first connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in compression, while that portion of the first and second flex link assemblies that is between the second connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in tension. Now consider the case where the actuator assembly is moving in the second direction and which places the coupling in compression. In this case, that portion of the first and second flex link assemblies that is between the first connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in tension, while that portion of the first and second flex link assemblies that is between the second connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in compression.
One advantage of the configuration of the connector that is utilized by the seventh aspect is that it enhances one or more aspects of the manner in which the motion of the coupling is transferred to the lever assembly. As discussed above in relation to the fourth, fifth, and sixth aspects, certain configurations for the coupling also may provide one or more advantages in relation to the transfer of forces to an elevation structure. Therefore, any of the features discussed above in relation to one or more of the fourth, fifth, and sixth aspects of the present invention may be used alone or in any combination with the subject seventh aspect (and vice versa).
An eighth aspect of the present invention is embodied by a microelectromechanical system that is fabricated using an appropriate substrate. A lever assembly is interconnected with this substrate such that at least part thereof is able to move both at least generally away from and toward the substrate, depending upon the direction of the force being exerted on the lever assembly. In this regard, the microelectromechanical system further includes an actuator assembly that is interconnected with the substrate for movement along a first path, a coupling that is appropriately interconnected (directly or indirectly) with this actuator assembly, and a connector that is attached to the lever assembly, and that is also attached to the coupling. As such, movement of the actuator assembly relative to the substrate is transmitted to the lever assembly through the coupling and the connector. Part of the connector is in compression and part of the connector is in tension, regardless of whether the actuator assembly is moving in the first or second direction in the case of the eighth aspect.
Various refinements exist of the features noted in relation to the eighth aspect of the present invention. Further features may also be incorporated in the eighth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. One appropriate configuration for the connector includes first and second connector ends that are spaced in the direction of the elongation or length dimension of the coupling (e.g., longitudinally spaced). The second connector end is located between the first connector end and the actuator assembly, and the coupling is attached at least to at least the first connector end (e.g., the coupling may also be attached to the second connector end). The connector may also include first and second flex link assemblies that extend between the first and second connector ends on opposite sides of the coupling, and first and second interconnects that extend from the first and second flex link assemblies, respectively, to different portions of the lever assembly. Movement of the actuator assembly in the first direction may move part of the lever assembly (e.g., a free end(s) of the lever assembly) at least generally away from the substrate and may place the coupling in tension. In this case, that portion of the first and second flex link assemblies that is between the first connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in compression, while that portion of the first and second flex link assemblies that is between the second connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in tension. Movement of the actuator assembly in the second direction may move part of the lever assembly at least generally toward the substrate (e.g., a free end(s) of the lever assembly) and may place the coupling in compression. In this case, that portion of the first and second flex link assemblies that is between the first connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in tension, while that portion of the first and second flex link assemblies that is between the second connector end and where the first and second interconnects merge with the first and second flex link assemblies, respectively, may be in compression. Each of features that were discussed above as being relevant to the seventh aspect also may be utilized by this eighth aspect as well, alone and in any combination.
A ninth aspect of the present invention is embodied in a microelectromechanical system that is fabricated using an appropriate substrate. A lever assembly is interconnected with this substrate such that at least part thereof is able to move both at least generally away from and toward the substrate, depending upon the direction of the force being exerted on the lever assembly. In this regard, the microelectromechanical system further includes an actuator assembly that is interconnected with the substrate for movement along a first path, a tether or coupling that is appropriately interconnected (directly or indirectly) with this actuator assembly, and a connector that is attached to both the lever assembly and the coupling. As such, movement of the actuator assembly relative to the substrate is transmitted to the lever assembly through the coupling and the connector.
Various refinements exist of the features noted in relation to the ninth aspect of the present invention. Further features may also be incorporated in the ninth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. In one embodiment, the connector of the eighth aspect includes at least one flex link or a structure that will flex more than the lever assembly when exposed to the types of forces exerted on the connector during normal operation. In another embodiment, at least one flex link of the connector is placed in compression and at least one flex link of the connector is placed in tension, regardless of whether the coupling is being placed in tension or compression by a movement of the actuator assembly. Stated another way, at least one flex link of the connector is placed in compression and at least one flex link of the connector is placed in tension, regardless of which direction the actuator assembly is moving relative to the substrate. In yet another embodiment, at least one flex link of the connector on each side of the coupling is placed in compression and at least one flex link of the connector on each side of the coupling is placed in tension, regardless of which direction the actuator assembly is moving relative to the substrate.